Hybrid electric vehicle (HEV) systems use an electric motor in conjunction with an internal combustion (IC) engine to drive a vehicle. In particular, range extender hybrid vehicle systems, such as plug-in hybrid electric vehicles (PHEV), utilize the electric motor as the primary source of propulsion. The electric motor draws power from an energy source, such as a battery. The IC engine, on the other hand, is primarily used to drive a generator, which, in turn, recharges the energy source. By using the IC engine to recharge the energy source, the range of the PHEV can be extended.